I've got an iMac running High Sierra, and over the last couple of months it has developed a problem where it spontaneously reboots itself about once a day.

The reboots always occur when the iMac is asleep and the pattern is always the same. When the reboot happens, the startup chime happens twice in close succession. The error message is always like this:

I researched Sleep Wake Failure on Ask Different and elsewhere on the web. I tried several things, including:

Energy Saver: Prevent computer from sleeping automatically when the display is off

Reset PRAM/NVRAM

Reset SMC

This iMac is getting a little old and it is quite possible a problem has developed with the hardware, but I do recall this started around the time I installed High Sierra and I've been assuming it's a correctable software problem.

Anyone have a fix yet? The High Sierra update has given me the same issue of the Sleep Wake Failure as well as dropping my wireless connection on and off constantly. I was hopeful that the 10.13.3 update fixed these known issues, but no. Very frustrating!
– Kelly RiesbergFeb 7 '18 at 22:49

Actually I do have an update. Recently I moved to a new house. Immediately the spontaneous reboots stopped happening. Same computer, same cords, same peripherals, same everything, except new house. This has me thinking now that it may have been some sort of power surges or brownouts relating to the electrical system in the old place. It's the only thing that seems to make sense. It's not a solution, but I hope this helps.
– robbpriestleyJul 12 '18 at 4:09

Is it also possible there is an important difference in your network environment between these 2 locations? For example: WI-Fi in one nd not the other, Bluetooth in one and not the other, Ethernet connection in one place and Wi-Fi in the other? My hypothesis is that this wake failure may be related to a bad managment of power consumption.
– danJul 30 '18 at 11:46

Yes, definitely possible but I do not suspect it as I used the identical network environment and equipment (Wifi router) both before and after the move.
– robbpriestleyJul 30 '18 at 15:06

Power Nap and Wake for Ethernet Access are already both disabled.
– robbpriestleyDec 11 '17 at 14:10

3

I have the same problem and this didn't work either
– SaudiBombsYemenJan 23 '18 at 13:41

I think that the 2nd change: "Wake for ethernet network access" avoid the sleeping state which is where the problem occurs. This is not fixing the problem but rather hiding it.
– danJul 30 '18 at 11:55

Power Nap is already disabled so that's not it, and although preventing sleep would most likely correct the problem, poor power management is not an acceptable solution for me either.
– robbpriestleyFeb 9 '18 at 3:00

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